Can someone please teach me about lenses?

Discussion in 'Beyond the Basics' started by manda, Feb 11, 2004.

  1. manda

    manda instigator of pottymouthedness

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    I am looking to purchase a new lens in the future but Im a big researcher before making a choice and Ive really got no idea what Im looking at.

    Could someone explain exactly what all the focal length numbers and other numbers mean? Whats a fixed focal length?

    Plus, do particular brands only fit certain cameras? I have a Canon EOS 300 and am wondering if Sigma lenses fit?

    Im wanting it to do portraits and macro mostly.

    Any help or suggestions of good lenses would be muchly appreciated.

    Thank you
     
  2. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Some of the answers are here

    http://www.thephotoforum.com/forum/viewtopic.php?t=3362

    Fixed focal length means it stays at one focal length as opposed to a zoom lens, which has adjustable focal length. In consumer lenses fixed focal length lenses (also called prime lenses) are usually faster (aperture opens up wide to allow more light in/ less DOF) than zoom lenses.

    Canon AF 35mm SLR cameras require a Canon EOS lens mount, manual focus Canons require the old FD mount, Nikon requires a Nikon lens mount, Pentax uses K mount, etc... Sigma, Tamron, and other brands market their lenses with a variety of mounts. Just make sure you get the right one for your camera.

    Macro work will require a macro lens or close up filters. Macro lenses can also be used for "regular" photography. Don't be fooled by "sales speak"; it is only a real macro lens if it offers 1:1. This means if you take a photo of a coin you could lay the coin next to the neg, and it would be exactly the same size. Many companies advertise telephoto lenses as macro; they are not real macro lenses, although they may do what you need them to do. True macro lenses will probably run about three times the cost of a similar focal length non-macro lens.

    For 35mm portraits I use 50mm focal length for shots that include the body, and try to go at least 70mm+ (preferably 90mm) for faces and head shots. This is where a zoom can be very handy (like a 28mm to 105mm).

    If you are trying to get one lens that would allow you to do both, I'd look for a macro lens with a fixed focal length of somewhere in the 90 to 105mm range. I know Tamron has an excellent one for about $600.
     
  3. tr0gd0o0r

    tr0gd0o0r New Member

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    I agree with Kmat here, except about his focal length for portraits. I'd suggest about 135mm lens. It gives you the ability to get further from the subject and thus gets them a little less nervous about having a camera in their face. Also you can get the closer shots if you need to.


    ::braces for big long technical explanation for why I'm wrong::
     
  4. Dew

    Dew New Member

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    mostly i use my "standard" zoom lens for most portraits .. i guess it depends on the lighting situation ... for the past few days, i've been shooting portraits under very poor lighting conditions ... i take about 4 lenses with me and always end up using my 50mm prime lens .. its super fast and give me nice shutter speeds .. since i dont always like to use a tripod :lol: .. its small and looks funny but i use it the most :D ... til the hubby surprised me with a 75mm-300mm zoom :D ... stealth like no other :eek:
     
  5. Harpper

    Harpper New Member

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    I've always wonder about the lenses myself. It's been a very long time since I've used one, but I was always curious as to when I should use a zoom lense as oppose to a prime lense. Since I'm in the process of saving up for a DSLR this topic really interests me.

    In the past when I've used film SLR, I've mostly used zoom lenses mainly because I like taking scenic pictures. It's a pain to hike a mile or more just to get the picture I want so a zoom lense is ideal. The problem was I was also using the same zoom lense for portaits and I'm now wondering if I put myself at a quality disadvantage. Can you really tell the quality difference or can only professionals see the difference? Also is there a lost in quality when I take pictures at the far zooming ends of the lense? I remember reading something about that. Normally I would just test it out myself but I no longer have access to the film SLR.

    Oh, one more thing before I forget. What's the best lense for low lighting?
     
  6. Dew

    Dew New Member

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    i've heard u can tell the difference and if the range is too wide, the quality goes down a tad :?

    i use this zoom 75mm-300mm for street stuff .. i dont have to get on top of my subject .. i can be a street away and almost hit their face in full frame (just got it 2 days ago, still experimenting on my film SLR) .. but mostly i guess its for sports and stuff, where u cant get too close .. im using it for street stealth photography :twisted: .. i wouldnt use it for a portrait lens
     
  7. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Once upon a time zoom lenses probably were inferior to prime lenses in terms of sharpness. This is not the case anymore. If you buy a good quality zoom lens it will compete very nicely with a good quality prime lens in terms of sharpness. Most of the criticisms of zooms' sharpness comes from pre 1990s experiences. I have a late 90s Pentax 28-200 zoom that I've blown up Tmax 100 negs to 16x20, and they are amazingly sharp. There is going to be a sweet spot somewhere in the range of focal lengths that is the absolute sharpest, but even at the ends a quality zoom will be very sharp. Once the engineers and factories got access to powerful computers it became very easy to figure out the problems and correct them.

    There are other issues than sharpness though.

    Lens flare: every glass to air surface among the lens elements can reduce color saturation a bit (a tiny bit), and increase lens flare potential. Zooms have many more elements than prime lenses, so they have the potential for more flare.

    Speed for your buck: You can find fast (f/2 or better) primes quite reasonably priced. Zooms faster than f/4 or f/5.6 though usually cost $1000+. This can be a big deal if you are into available light photography. Also, most lenses are sharpest 2 or 3 stops from wide open, so if this is where you like to shoot it turns your f/2 50mm into an f/4, and your f/4 28-105 into an f/8, which may mean shooting ISO 400 instead of ISO 100.

    Learning curve: I think that zooms get in the way of learning about focal length. Most beginners spot the image, and then crop with the zoom, not paying attention to the focal length they are using. They never get a feel for how focal length affects the image. The right way is to spot the image, decide on a focal length, set the focal length, and then crop by moving closer or farther away from the subject.

    If I could only have 2 lenses for my 35mm SLRs I would pick a 28-200 (or even 28-300) zoom and a fast 50mm prime.

    I don't know exactly when he wrote this, but here is a quote from Ansel Adams "The Camera" (<--THE BOOK on how film cameras operate, and would probably even teach a thing or two to digital only folks).

    "In earlier years some lenses were definately superior to others; their images proclaimed their differences. I have a Voightlander 12" process lens that is suberb, despite it's age of more than 70 years, and I have done some of my best work with Zeiss Protars, nearly 40 years old. More recently, the computer has moved into the industry, and practically all lenses made within the last decade or two are excellent-often more precise than even the most exactingpractical photographer requires. They are, in fact, usually better in their capacity for preserving fine detail than our standard contemporary films and papers can record."
     
  8. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    No technicalities here, it's just that I am always right and you are always wrong :wink: just kidding!!!

    When I said "preferably 90mm, I should have said "preferably 90mm+". 135mm works for me. The more telephoto you go, the more of a flattening effect you will see, but this is better than going wide, which emphasises the distance between facial landmarks such as nose, cheek bones, and ears. This can make folk look big nosed and wide faced; this isn't usually complimentary to most people.
     
  9. Harpper

    Harpper New Member

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    Thanks for the info ksmattfish. I found it very helpful.

    Yes, that's why I like digital so much and not only in photography. People may not see the huge difference in quality when their images are printed out but the "left over fine detail" from a high megapixel camera shown on a large resolution computer monitor (1024x768 and above) comes out super sharp. The sharpest pictures I've ever seen are from the computer monitor. Although you do have to have a good monitor. I'm studying to be a computer graphics designer, so I see the difference between print and computer graphics on a daily basis. There is an amazing amount of detail you can add to digital graphics but they don't transfer into printed images all too well. As Ansel Adams stated, we aren't there yet with tangible graphics.

    On a side note, that's why I like to sometimes watch DVD movies on my computer monitor as opposed to my tv. The sharp quality of DVD is wasted on a standard tv in my opinion.

    To get an idea of what I'm talking about, you guys can check out this site: http://www.dpreview.com/gallery/. Make sure to look at the pictures from top DSLR cameras to see what I mean. This shot taken with a Canon EOS 300 Digital Rebel in particular stood out for me: http://img.dpreview.com/gallery/engine.asp?photo=4&gallery=canoneos300d_samples
     
  10. voodoocat

    voodoocat ))<>((

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    A print is superior in every aspect over a computer monitor. There is no super-monitor that can display more detail than a good print. I think a lot of people forget about the print. Especially these days with everything being digital. Even most modern inkjet printers can print sharper than the eye can see.

    In conclusion, print > monitor.
     
  11. Harpper

    Harpper New Member

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    I guess this topic is subjective because I still think some of the stuff I've seen on my monitor is better than the quality prints I've seen but then again I have a "Professional Series" monitor. I'm not saying I can't be wrong but I really like the detail I get from my monitor as oppose to printed photos. I'm sure it comes down to differences in tastes.
     
  12. voodoocat

    voodoocat ))<>((

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    Well aside from taste there is a technical side that says one is better than the other. Yes, there is a certain luminosity when viewing an image on the monitor. Check out a slide projected on a nice sharp screen you can get even better results and still get that glow. Prints (I'm talking good prints) display a larger range of tones and resolve finer detail than the most expensive monitor.

    I'm thinking you're not comparing apples to apples. If you're viewing a fully enlarged image on your screen and looking at a 4x6 yes, the monitor will appear sharper. What is the control element of your observance? Are you comparing a print from walgreens, print from a pro lab with a pro that makes money for making good prints.... or are you printing from a deskjet or dye sub or...

    Another very important factor to take into consideration is the anti-alias element found in most every digital camera out there. To make a good print (in most cases) you would want to use 100-150% unsharp mask.
     
  13. Harpper

    Harpper New Member

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    I'm mostly talking about photos from "Walgreens" type labs, but I do compare them proportional to their sizes...ie; a 4x6 print on paper and on the monitor(not a fully enlarged image but proportional pixel-wise). Although even with that being said, I have paid for professional portraits and had them developed in quality pro labs so I have seen high end stuff. I'm not saying the quality prints I've seen aren't sharp but there's still something about graphics on the monitor.

    I think the luminosity you are talking about might be what I'm talking about. Graphics on the monitor have a different look to them which I like. Both the high end prints and digital images are very sharp but there's something about the monitor that tricks my mind into thinking it's sharper. I can't quit put my finger on it but I just like the images from my monitor. I'm sorry I even brought this up because it really sounds subjective.
     

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